Circuits



y 1945. v. G. VAUGHAN 2,375,967

CIRCUIT Filed Jan. 24, 1941 Patented May 15, 1945 CIRCUITS Victor G.Vaughan, Attleboro, Mass, assignorto Metals & Gontrols Corporation,Attleboro. 'Mass., a corporation of Massachusetts Applicationd'anuary24, 1941, Serial No. 375,805

(Cl. 3l5--100) 4 Claims.

This invention relates I to thermostatically controlled electriccircuitsandrmore particularlyto switch circuits for starting'fiuorescenttubelights.

An object of thisinvention is .to-providea thermostatically controlledstarting switch circuit for starting so-called fluorescent ligh tubes orlamps. Another object of .theinvention is-to p'ro vide a circuit whereinonly two wires are needed to connect thestarting switchto the circuit inorder to accomplish the starting of the lamp. Other objects WilLbeinpartobvious andin part pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, and arrangements of parts which will be exemplified in thecircuit hereinafter described, and the scope of the application of whichwill be indicated in the following claims.

In the accompanying drawing, in which are illustrated several of thevarious possibleembodiments of the invention,

Fig. 1 is a diagram of a circuit embodyingthe present invention;

Fig. 2 is a diagram of a similar circuit but employing a different-typeof thermostatic element;

Fig. 3 is a diagramoi a similar circuit embodying a still different typeof thermostaticelement; and,

Fig. 4 is a diagram of a similar circuit but embodying a still differenttype ofthermostat'ic element.

Similar reference characters indicate correspending parts throughout'theseveral views of the two electrodes are customarily placed in serieswith a choke coil across the power lines. After a given interval of timenecessary to heat the electrode the interconnection between theelectrodes electrodes can be done in many ways, but it is the purposeofthis invention to provide a simple thermostatic switch circuit for thatpurpose.

The preferred thermostaticswitch for use in this invention is that shownand described inJohn D. Boleskys United States Patents 2,199,387 and2,199,388. However, any thermostatic switch of similar nature can beused to accomplish the purpose of .the present invention. Brieflydescribed, the preferred switch is as iollowszA base made ofelectrically insulating material is provided having a circular rim andan upstanding skirt thereon. Mounted on an adjusting screw passingthrough the center of the baseis a thermostatic snap-acting disc such asis described and shown in John A. Spencer's Patent 1,448,240. Thedisc ismounted on the adjusting post by means of the usualaoutments andshoulders so as to provide a secure, yet not binding, mounting of thedisc. Contact buttons are welded or otherwise electrically fastened tothedisc on diametrically opposite points on its periphery, to cooperatewith stationary contacts passing through holes in the base and. clampedtherein, or otherwise fastened. A third stationary contact is providedand is similarly fastened to the base I. A heater wire is fastened atone end to the third stationary contact and at'it's otherend to one ofthe other stationary contacts. This switch and its operation aredescribed in detail in John D. Boleskys patents above referred to.

Referring now to Fig. l of the drawing, numeral 3 indicates generally athermostatic switch comprising asnap-acting disc 5, movable contacts Gand] mounted on disc 5, and stationary contacts 8 and 9 cooperating withcontacts Sand 1 to open and close the electrical circuit,'and stationarycontact H The heater wire I! for the-thermostat is connected betweenstationary contacts 8 and it. Such a switch is fully described in theaforesaid Patents Nos. 2,199,387 and 2,199,388.

Numeral l2 indicates, in'general, the outer wall of a conventional typefluorescent lamp. Sealed into the ends of this lamp are the twoelectrodes l3 and I l. Power line It is connected to one side of theelectrode iii-through a choke coil'l5. Power line ll is connected to oneside of the electrode i l. The other side of electrode 13 is connectedto stationary contact It. The other side of electrode it is connected tocontact 9. Permanently shunted across stationary contacts 8 and dis'anexternal resistance 18.

In this circuit, the choke coil I5 is used for two purposes as described.above: First, to provide a momentary high-voltage discharge to ignitethe lamp when the thermostatic disc opens, and secondly, to limit theamount of current which flows through the lamp.

The operation of the circuit is as follows: When line switch 59 isclosed, current flows through wire 26, electrode l4, wire 2!, disc 5,heater wire I I, wire 22, electrode 13, wire 23, choke coil l5, and tothe power line It. The electrodes l3 and M commence to heat, and heaterwire ll commences to heat up disc 5. Within two or three seconds, disc 5snaps to its upward (circuit opening) position, thus opening theinterconnection between the'electrodes through wires 2i and 22. Thisopening of the circuit causes a momentary, induced, relatively high.voltage to be impressed across the tube from electrode IE to electrode Il and starts the gaseous discharge. This discharge between theelectrodes causes the fluorescent coating of the tube to glow and givethe light for which the lamp is designed. noted that when the disc 5 isin its closed position, the electrical resistance i8 is shunted out ofthe circuit since its resistance is relatively very high in comparisonto the resistance of the disc 5. However, when disc 5 opens, heater wireI8 is now in the circuit and current now passes through the electrodes,electrical resistance l8, and heater H. However, resistance It ispurposely of such value as to reduce the current passing through theelectrodes to a very low value. This low current allows heater wire H togenerate just enough heat to keep the disc 5 in its switch-open positionwhile the tube is lighted. When the switch is is opened, the gaseousdischarge ceases and the tube no longer fluoresces.

Heater l I now has no current flowing through it, so it cools down, anddisc 5 likewise cools to snap back to the switch-closed position. Thecircuit is then ready for relighting the lamp.

Any other form. of simple thermostatic switch may be employed in thisinvention, as well as ambient compensated types such as shown forexample in Harold M. Wilson's United States Patent No. 2,203,558.

A simple strip type composite metal thermostat is shown in Fig. 2. It ismounted at one end in any suitable manner as shown at 26. The oppositeend carries a movable contact 2'! which cooperates with a fixed contact9. The relatively high resistance I8 is as before shunted around thecontacts. in this instance, movable contact 21 and stationary contact 9.The heater H is connected to movable contact 21 as shown and is locatedso as to control the strip type thermostat 25. The circuit operates in amanner similar to that of the Fig. 1 circuit. Movable contact 2'! andstationary contact 9 are held in contact by strip 25 when the device iscold. Upon closing switch is the current passes through the contacts 9and 21 and through heater H until strip 25 is heated sufficiently tobreak the circuit. The current thereupon passes through the highresistance iii to movable contact 2? and heater l i at a rate sufficientto cause thermostatic strip 25 to maintain contact 21 away from contact9.

Fig. 3 illustrates a circuit embodying an am bient compensated type ofthermostat such as is shown and described for example in Harold M.Wilsons United States Patent No. 2,203,558. The thermostatic element 28in this instance is composed of two composite metal snap acting discs 29and 30. The outer edges of these discs are preferably mounted so as tobe relatively immovable as shown at 3| and 32. Such a mounting is,

It is to be together.

however, arranged to be suificiently loose so that the discs can snapback and forth freely. The centers of the discs are held together by anysuitable means as shown at 33 so that they move The discs 29 and 30 areoperatively associated with arm 43 which is made of spring metal. Theconnection 33 between the discs is elongated as shown at 4| so as tocontact an in sulating sleeve 42 which sets into an opening 43 in thearm All. Insulating member 42 is headed over as shown at M where itcontacts portion M of connection 33. The arm carries a contact 45 whichcooperates with contact 46 mounted on stationary arm 41. The tension inarm. 40 is arranged so that the arm tends to move contact 4-5 out ofengagement with contact 66. When the discs 23 and 3B are in the positionshown in Fig. 3.

. however, they, through connecting member 33.

and insulating member 42 force arm 4!? against the tension thereof intoposition so that contacts and it are in engagement,

When the discs 29 and 30 snap into the opposite position of concavitydue to heat from the heater wire H the portion 4| of connecting member33 no longer keeps the arm 40 in a position such that the contacts 45and 46 are in contact. The

inherent tension of arm 40 then separates the contacts 15 and 45. Thecurrent then passes through resistance l8. Inasmuch as the constructionand operation of an ambient compensating device such as indicated isclearly described and explained in the aforesaid Letters Patent, it willnot be repeated here.

It will be noted that the current path is through the wire 2i, arm at,contact 46, contact &5, arm id, heater H, and wire 22 when the device isin the Fig. 3 position. When the discs 29 and 39 snap to the oppositeposition the current path is from wire 2! through resistance l3, arm 49,heater H, wire 22. The heater II is located so to affect disc 3Q morethan disc 29. The passage of current through heater H causes disc 38 toover balance disc 29 and open contacts 35 and 46. When the contacts areopen, a small amount of curent is carried by resistance iii to heater Ii and keeps the disc 30 at a relatively higher tempera ture than disc29.

A still further embodiment of the invention is illustrated in Fig. 4.This likewise employs an ambient compensated thermostatic switch. Thethermostatic switch in this instance comprises two composite metalstrips of thermostatic material 3&- and 35. They may be mounted in anysuitable manner at one end as indicated at is and 3?. Cooperatingcontacts 38 and 33 are attached to the opposite ends, that is, themovable ends of the thermostatic strips. Strips 3d and 35 areconstructed so that they will maintain the contacts 38 and til togetherduring variations in ambient temperature, since they have the samerelative response to changes in ambient temperature. I-Ieatcr llhowever, is positioned so as to affect one of the strips. in thisinstance to a greater extent than the other strip. Accordingly, whencurrent passes through the circuit when contacts 38 and 39 are together.it passes through the heater ll likewise, thereby imparting a relativelygreater movement to strip 35 than to strip 36. Strip 35 therefore movesa greater distance than strip 34 and separates the contacts 3f! and 39.The current is then shunted around the contacts 353 and 39 and passesthrough resistance Hi. It will be noted how ever, that the current stillpasses through heater H so that strip 35 is kept at a relatively highertemperature than strip 34 and contacts 38 and 39 are maintained apart.

Similarly other forms of thermostatic switches may be employed in thisinvention with only relatively minor changes in the circuit,

Among the advantages of the invention are (1) the need of only two wires(2! and 22) to connect thestarting switch to the lamp, which makes forease of wiring and installation; and (2) the fact that when the lamp islighted the heat holding disc 5, strip 25, or the like in circuit-openposition is just enough for this purpose; this means that when the mainline switch I9 is opened to shut off the lamp, disc 5 immediately.

cools to circuit-closed position. Thus, the delay necessary before thelamp can be reignited by means of switch I9 is reduced to a minimum.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A circuit comprising a fluorescent light source, a thermostaticswitch characterized by having only two lead wires, said switch beingconnected across the electrodes of said light source, an electricalheating resistance connected in series with said thermostatic switch andadapted to heat said switch, and a relatively high resistance connectedacross the contacts of said switch, said switch comprising a snap-actingthermostatic element.

2. A circuit comprising a fluorescent light source, a thermostaticswitch characterized by I having only two lead wires, said switch beingconnected across the electrodes of said light source, an electricalheating resistance connected in series with said thermostatic switch andadapted to heat said switch, and a relatively high resistance connectedacross the contacts of said switch, said switch comprising athermostatic element.

3. A circuit comprising a fluorescent light source, a thermostaticswitch characterized by having only two lead wires, said switch beingconnected across the electrodes of said light source, an electricalheating resistance connected in series with said thermostatic switch andadapted to heat said switch, and a relatively high resistance connectedacross the contacts of said switch, said switch comprising a creep-typethermostatic element.

4. A circuit comprising a fluorescent light source, a thermostaticswitch characterized by having only two lead wires, said switch beingconnected across the electrodes of said light source, an electricalheating resistance connected in series with said thermostatic switch andadapted to heat said switch, and a relatively high resistance connectedacross the contacts of said switch, said switch comprising an ambientcompensated thermostatic element.

VICTOR G. VAUGHAN.

